The present invention relates generally to traffic flow control and specifically to a system and method for controlling traffic routing and flow.
Today, vehicle drivers generally use paper maps, or in some cases electronic maps, to guide them to their destinations. In other cases a driver may be shown the route either by one giving them directions or driving the route. Once a driver no longer needs directional guidance than he/she may follow the route based upon routine or habit. Thus, drivers select their routes based on habit or routine, generally resulting in non-optimal use of the road network under actual conditions. This is because congestion information is typically not known to drivers and as a result they are not able to navigate so as to avoid the congestion. Anecdotal traffic and road condition information is occasionally available from radio broadcasts, and in rare instances by variable message signs that have been installed in the infrastructure. Such information sources, however, are sparse in the information that they convey and difficult for many drivers to act upon. In addition, road condition information is most often delivered too late to help in preventing major congestion; mostly the conditions that will cause congestion are not noted early enough.
For example, for a driver unfamiliar with an area, information such as xe2x80x9ccongestion aheadxe2x80x9d from a variable message sign will not provide sufficient information to allow the driver to alter his original route. Non-recurring congestion (e.g., traffic accidents) can cause immense traffic tie-ups and delays. If drivers upstream from these events had adequate information about the congestion and about alternative routes, however, the resulting congestion could be reduced. In addition, if a plurality of alternative routes are available, and if the drivers could be guided in such a way as to optimally use the alternative routes, then the congestion resulting from an incident, as well as from normal traffic patterns, could be greatly minimized.
There is also a type of recurrent congestion (due either to poorly designed roads, or overloading of roads, poorly timed traffic control devices, misuse of lanes, etc.). An example is a multi lane road with a turn lane where the turn lane is used by drivers to pass slower traffic and then merge back into non-turning traffic. These points are analogous to ice crystals forming in supercooled water-drivers that are slower to respond (i.e., traffic works on a lowest common denominator-thus one slow reacting driver creates rippling/magnifying delays for all of the other drivers).
U.S. Pat. No. 5,172,321 teaches a method by which dynamic traffic information is communicated to vehicles over a wireless modality so that route selection algorithms in the vehicle can select an optimum route. This is an improvement, but can itself result in unstable traffic flow. Each vehicle receives the same information, and drivers have no knowledge of the route selections of other drivers, allowing the likely possibility of subsequent traffic instability (e.g., traffic jams) if many vehicles choose the same alternate route based on the same information. This system requires a high bandwidth to communicate all dynamic traffic data to all vehicles in areas with a dense road infrastructure. As a result, to be practical, the system must limit its information broadcast to traffic conditions of the most heavily traveled routes.
As can be seen, a need has arisen for a system for determining optimal traffic flow based upon current and projected traffic and road information, and for communicating that information to vehicles.
U.S. Pat. No. 5,619,821 entitled xe2x80x9cOptimal and Stable Planning Systemxe2x80x9d addresses this problem by providing a system for determining optimal vehicle routes using current traffic flow information received from individual vehicles. The system comprises one or more fixed computers connected via a wide area network, the computers storing a model of a road network specifying the geometry of road segments and traffic characteristics of the road segments; communication means allowing fixed and wireless communication between the fixed computers and mobile in-vehicle computer units, and also fixed communication among the fixed computers; means in the fixed computers for computing an optimal route for each vehicle based upon data supplied by the in-vehicle units; and means for communicating optimal route information to the in-vehicle units.
Although the system works effectively for its stated purpose, as is noted it computes the optimal route based upon in-vehicle information, but does not necessarily take into account other issues that may arise, apart from information by the vehicles. For example, an emergency may occur that is not generally known, such as an impending storm, hurricane or other naturally occurring disaster. In addition, there may be some other type of emergency, such as a fire or the like, that may require a change in traffic flow or the like.
There are other issues with traffic control which are not addressed by the above-cited references. Accordingly, it would be desirable to allow an owner of a vehicle to control the use of a vehicle by another. For example, it would be desirable for a parent to automatically control the use of an automobile by his/her child. In another example, it would be desirable for a rental car to automatically control the use of their cars by the people who lease the cars. Finally, in a third example it would be desirable to allow a governmental authority, such as the court, to automatically control the time and distance that an individual can drive a vehicle if the individual has been convicted of a crime such as drunk driving. None of the above-identified systems address these problems.
What is needed is a system to overcome the above-identified problems. The present invention addresses such a need.
A hierarchical traffic control system is disclosed. The traffic control system comprises a primary controller. The primary controller receives information about traffic in an area. The system further includes a plurality of subsidiary controllers. The subsidiary controllers provide information to and receive information from the primary controller. Each of the plurality of subsidiary controllers is associated with a cell within the area. Each of the subsidiary controllers receives and provides information to at least one vehicle concerning traffic conditions within its associated cell. The primary controller and each of the subsidiary controllers are capable of negotiating a change in the flow of traffic based upon traffic conditions.
In a method and system in accordance with the present invention, each of the traffic controllers monitors a finite portion of the route and can be in direct contact with the vehicles. The primary traffic controller receives and transmits information to and from the traffic controller and allows for an overall view of the route to be understood. Accordingly, through the use of the hierarchical traffic control system, traffic is controlled from cell to cell more accurately and can be controlled over a wide traffic span.